JP3462628B2 - Superconducting accelerating cavity - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cavity body and a cryogenic liquid storage tank used for a superconducting acceleration cavity for accelerating charged particles.

[0002]

2. Description of the Related Art Superconducting cavities are used as experimental devices for accelerating charged particles 13 such as electrons and positrons to near the speed of light in the study of elementary particle physics, for example. A conventional superconducting accelerating cavity is shown in FIGS.

In FIG. 5, 1 is a superconducting material (for example, pure N).
It is a hollow body manufactured from the material b). In order to maintain the superconducting state, the cavity body 1 needs to be in a cryogenic state near -269 ° C.

Therefore, the cavity body 1 is mounted inside the cryogenic liquid storage tank 2, and the cryogenic liquid storage tank 2 is filled with the cryogenic refrigerant 3, for example, liquid helium. The cryogenic refrigerant 3 generally has a very low boiling point, for example, -269 ° C. in the case of liquid helium, and in order to suppress the evaporation amount of the refrigerant, the amount of heat entering the cryogenic liquid storage tank 2 from the surroundings is reduced as much as possible. There is a need to. Therefore, the cryogenic liquid storage tank 2 is installed in the vacuum heat insulating container 4 to perform vacuum heat insulation and reduce the amount of heat entering.

On the other hand, at both ends of the cavity body 1, charged particles 1 are
The beam pipe 5 serving as the passage 3 is connected. FIG. 6 shows details of a connection portion of a conventional beam pipe.

The hollow flange 7 made of a superconducting material such as niobium and the beam pipe flange 8 made of stainless steel are connected to the bolt 1 via the fastening flange 6.
It is concluded with 0.

Further, indium 9 is used as a sealing material for this portion. An ultrahigh vacuum is required inside the cavity 1 and the beam pipe 5, and the indium 9 achieves the airtightness of the refrigerant 3 and the ultrahigh vacuum.

In the case of the seal of the cryogenic liquid storage tank 2 as described above, the packing made of a usual rubber or synthetic resin material becomes brittle even at a low temperature and hardly usable. Therefore, indium 9 which is a pure metal and whose characteristics do not change even at an extremely low temperature and is very soft is generally used.

Indium 9 has a sealing effect due to strain due to plastic deformation, unlike ordinary packing which is deformed within the elastic limit to ensure airtightness. However, due to deterioration over time, the surface of indium becomes brittle and airtightness deteriorates. To do.

Therefore, the cryogenic refrigerant 3 leaks to the inside of the beam pipe 5, the degree of vacuum inside the beam pipe 5 deteriorates, and the operation of the superconducting acceleration cavity must be stopped. .

In the conventional technique, after the operation is stopped, the joint portion is disassembled and the indium 9 is replaced with a new one to obtain airtightness. However, when disassembling and reassembling, the old indium 9 is removed from the flange surface. The removal work requires a great deal of time and attention, and results in a decrease in experimental efficiency.

Further, as shown in FIGS. 7 to 8, the indium seal 9 is also used as a sealing material between the input coupler flange 14 and the cavity flange 7 and a sealing material between the 15D port flange 15 and the cavity flange 7. Since they are used, these joints have similar problems.

[0013]

According to the prior art, in the beam pipes 5 provided at both ends of the cavity body 1,
Since the sealing property of indium used in the fastening portion of the cavity flange 7 made of niobium material on the side of the cavity body 1 and the beam pipe flange 8 made of stainless steel deteriorates due to deterioration over time, the cryogenic refrigerant 3 is used as the beam pipe. Leak inside 5.

Therefore, the cavity body 1 and the beam pipe 5
There is a problem that the degree of vacuum inside deteriorates and the operation of the superconducting acceleration cavity must be stopped. The same problem is caused by the input coupler flange joint and 15
It also occurs in the indium seal 9 at the D port junction. It is an object of the present invention to provide a superconducting accelerating cavity that can solve these problems.

[0015]

In order to solve the above-mentioned problems, the present invention comprises a cavity body (1) and a cryogenic liquid storage tank (2) .
Of the cavity body (1) is opened outside the cavity body (1)
Opening part and corresponding cryogenic liquid reservoir (2) part
It is constituted in one piece by being brazing, the
Cavity body (1) in integrated cryogenic liquid storage tank (2)
The member arranged in the opening part of the metal O-ring (11)
Fixed with bolts (10) on the flange (6) sandwiching
Characterized in that so as to be.

Further, according to the present invention, the portion arranged in the opening portion
Wood is, and Bimupai-flops, the input coupler flange
When, characterized in that in the flange of 15D port.

[0017]

According to the present invention, due to the integral type , the reliability of the seal can be improved as compared with the conventional indium seal 9, and the refrigerant 3
Can be prevented from leaking into the cavity body 1 . B
Each part of the boom pipe, input coupler, 15D port
Integral by brazing
The reliability of the seal can be improved.

[0018]

EXAMPLE An example of the present invention is shown in FIGS. FIG. 1 shows the outer shape of the first embodiment of the present invention, and FIGS. 2 to 4 show the details of the connecting portion of the first embodiment.

The superconducting accelerating cavity body 1 is made of niobium, which is a superconducting material, by molding and electron beam welding.
It is manufactured in the shape shown in. Then, the end plate portion of the cryogenic liquid reservoir 2 made of stainless steel (for example, SUS316L) is processed so as to match the outer peripheries of the cavity beam pipe flanges 7 located at both ends of the cavity body 1.

Then, a brazing material (for example, a gold brazing material) is placed in the gap, placed in a vacuum furnace, heated and melted, and brazed and joined. Although the cryogenic liquid storage tank 2 is made of stainless steel as an example here, aluminum (for example, A5083 or A50) is used.
52) is also acceptable.

However, if niobium material is used for the cavity body 1, there is an advantage that the cavity body 1 and the cryogenic liquid storage tank 2 can be welded and joined, but the material cost becomes very expensive as compared with stainless steel and aluminum, and it is economical. Niobium has low mechanical strength (tensile strength of about 12 kg / mm ² , 0.2%)
Since the specific gravity is as high as 8.56 in comparison with the proof stress of about 9 kg / mm ² , the container becomes very heavy with a thick plate, and there is a drawback that it is difficult to handle when assembling the device and attaching the hem.

[0022] And, the end plate portion of the hollow beam pipe 7 which is joined by brazing cryogenic liquid reservoir tank 2 is connected to beam pipe flange 8, the structure of that portion is machined part of the end plate To make a sealing surface, and also to install a bolt tap hole for attaching a flange.

On the other hand, a gasket groove is formed on the beam pipe flange 8 side. The state in which they are combined is shown in FIG. The seal between the refrigerant 3 (generally, liquid helium is used) filled in the cryogenic liquid storage tank 2 and the inside of the beam pipe 5 through which the charged particles 13 pass is the above-mentioned seal. Airtightness is obtained by appendix 12.

The degree of vacuum inside the beam pipe 5 is in the range of 10 ⁻⁹ to 10 to maintain the life of the charged particles 13 as long as possible.
^-11 Torr ultra high vacuum is required. The inside of the vacuum heat insulating container 4 has a vacuum degree of 10 ⁻⁵ to 10 ⁻⁶ Torr,
During this time, it is necessary to ensure airtightness.

Therefore, as shown in FIG. 2, a metal O-link 11 is provided between the cryogenic liquid storage tank 2 and the beam pipe flange 8. Here, the reason why the metal O-link 11 is used is that the same joint portion has an extremely low temperature atmosphere.

Next, the input coupler connection portion and the 15D port connection portion will be described by taking the input coupler portion (FIG. 3) as an example. This portion is a nozzle (material made of niobium) provided vertically above the cavity body 1 and a cryogenic liquid storage tank input coupler flange 17
Brazing is performed 12 between (the material is stainless steel or aluminum).

The inside of the input coupler is an ultrahigh vacuum of the order of 10 ⁻⁹ to 10 ⁻¹¹ Torr in the same atmosphere as that of the inside of the cavity body 1, and the airtightness of the refrigerant 3 is maintained by the brazing 12 described above. .

Further, the vacuum heat insulating container 4 (the degree of vacuum is from 10 ^-5 to
The seal between the 10 ^-6 Torr) and the inside of the input coupler is the same as that of the beam pipe 5 at the metal O-link 11
It maintains airtightness.

The same applies to the structure of the 15D port connection portion.
The hollow body 1 and the cryogenic liquid storage tank 2 can be integrated by brazing different materials of niobium and stainless steel / aluminum in the above-mentioned ports and nozzles (FIGS. 2 to 4).

At this time, both are cooled from room temperature to an extremely low temperature of about -269 ° C., but thermal stress is generated due to the difference in linear expansion coefficient due to the integration of different materials. Therefore, a bellows 16 is provided near each joint to relieve the thermal stress.

With the above structure and function, the indium seal 9 used conventionally is eliminated and the brazed 12
Can be adopted, and the airtight reliability of the device can be improved. At the same time, a large flange at the beam pipe can be eliminated, and a compact and lightweight superconducting accelerating cavity can be realized.

[0032]

Since the present invention is constructed as described above, it has the following effects. (1) According to the present invention, the superconducting accelerating cavity, it is possible to improve the reliability of the seal than indium 9 of traditional. (2) Therefore, even if the superconducting accelerating cavity is operated for a long time (2 to 3 years or more), leakage from the joint can be prevented and stable physical experiments can be performed. (3) Also, indium seal 9 for brazing and joining
The thick plate flange that is required during use is unnecessary, and the cryogenic liquid storage tank 2 itself can be made extremely lightweight and compact. Therefore, it leads to low cost, and the handling and installation of the device assembling becomes easy.

[Brief description of drawings]

FIG. 1 is an outline view of a superconducting acceleration cavity according to a first embodiment of the present invention.

FIG. 2 is a detailed view of part A (beam pipe connection part) of FIG.

FIG. 3 is a detailed view of a part B (input coupler connection part) of FIG.

FIG. 4 is a detailed view of a C portion (15D port connecting portion) of FIG.

FIG. 5 is an outline view of a conventional superconducting acceleration cavity.

FIG. 6 is a detailed view of part A (beam pipe connection part) of FIG. 5;

FIG. 7 is a detailed view of a B part (input coupler connecting part) of FIG. 5;

FIG. 8 is a detailed view of a C portion (15D port connecting portion) of FIG.

[Explanation of symbols]

1 ... cavity body, 2. Cryogenic liquid storage tank, 3 ... Refrigerant, 4 ... vacuum insulation container, 5 ... Beam pipe, 6 ... tightening flange, 7 ... Hollow beam pipe flange, 8 ... Beam pipe flange, 9 ... Indium seal, 10 ... tightening bolts, 11 ... Metal O-link, 12 ... with brazing 13 ... Charged particles, 14 ... Cavity input coupler flange, 15 ... Hollow 15D port flange, 16 ... Bellows, 17 Cryogenic liquid storage tank input coupler flange, 18 ... Cryogenic liquid reservoir 15D port flange.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-5-266996 (JP, A) JP-A-7-22199 (JP, A) JP-A-7-111197 (JP, A) JP-A-7- 245199 (JP, A) JP 8-330098 (JP, A) JP 8-83698 (JP, A) JP 60-246600 (JP, A) JP 3-208300 (JP, A) JP-A-4-78175 (JP, A) JP-A-7-245198 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 7/20

Claims (2)

(57) [Claims] 1. A cavity body (1), a cryogenic liquid storage tank (2) in which the cavity body is mounted inside to keep the cavity body in a cryogenic state, a refrigerant (3), and a vacuum insulation container ( 4), wherein the cavity body (1) and the cryogenic liquid storage tank (2) are
The cavity body (1) is opened outside the cavity body (1).
Opening part and corresponding part of the cryogenic liquid storage tank (2)
Minutes and is configured in one piece by Rukoto attached low, this
In the cryogenic liquid storage tank (2) that is an integrated type of
The member arranged in the opening of (1) is a metal O-ring.
Bolting (10) of flange (6) with (11) sandwiched
A superconducting acceleration cavity characterized by being fixed at . 2. A member disposed in the opening portion, claims, characterized in that in (A) and Bimupai flop, (B) and Input coupler flange, the flange of the (C) 15D port 1. The superconducting acceleration cavity according to 1.